1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for recording, a method of manufacturing the same, and a magnetic recording apparatus in which a thin film magnetic head is mounted.
2. Description of the Related Art
In recent years, in association with improvement in areal density of a magnetic recording medium (hereinbelow, simply called “recording medium”) such as a hard disk, improvement in performance of a thin film magnetic head to be mounted on a magnetic recording apparatus such as a hard disk drive (HDD) is demanded. Known recording methods of a thin film magnetic head are a longitudinal recording method in which the orientation of a signal magnetic field is set to an in-plane direction (longitudinal direction) of a recording medium and a perpendicular recording method in which the orientation of a signal magnetic field is set to a direction orthogonal to the surface of a recording medium. At present, the longitudinal recording method is widely used. However, when a market trend accompanying improvement in areal density of a recording medium is considered, it is assumed that, in place of the longitudinal recording method, the perpendicular recording method will be regarded as a promising method in future for the following reason. The perpendicular recording method has advantages such that high linear recording density can be assured and a recorded recording medium is not easily influenced by thermal decay.
A thin film magnetic head of the perpendicular recording method has, mainly, a thin film coil for generating a magnetic flux and a magnetic pole layer for emitting the magnetic flux generated by the thin film coil toward a recording medium. In the thin film magnetic head of the perpendicular recording method, when current is passed to the thin film coil and a magnetic flux for recording is generated, a magnetic flux is emitted from the tip of the magnetic pole layer, and a magnetic field for recording (perpendicular magnetic field) is generated. Consequently, the surface of the recording medium is magnetized on the basis of the perpendicular magnetic field. In such a manner, information is magnetically recorded on the recording medium.
Improvement in the performance of the thin film magnetic head is in increasing demand. Considering such a technical background, recently, as a measure capable of improving the performance of the thin film magnetic head, for example, in addition to the change of the recording method from the longitudinal recording method to the perpendicular recording method, attempt to optimize the magnetic domain structure of a magnetic component of the main part of the thin film magnetic head is being examined.
Concretely, for example, a magnetic film having a magnetic layer made of a magnetic metal and a transition metal and an intermediate layer similarly made of a magnetic metal and a transition metal and optimized so that the composition of each of the magnetic layer and the intermediate layer can assure a high frequency characteristic, strong uniaxial anisotropy, and high saturated magnetic flux density is known (refer to, for example, Japanese Unexamined Patent Application (JP-A) No. 2000-150233). There is another known magnetic material containing nickel (Ni), iron (Fe), and molybdenum (Mo) and whose composition and magnetostriction constant are optimized so that a high frequency characteristic and an excellent magnetic domain structure can be assured (refer to, for example, JP-A No. 2000-235911).
Examples of known thin film magnetic heads include: a thin film magnetic head having a top magnetic pole in which magnetostriction constants in upper and lower regions are opposite to each other so that uniaxial anisotropy can be assured in an arbitrary direction (refer to, for example, JP-A Nos. H07-307009 and S61-192011); a thin film magnetic head having a yoke including two sets of magnetic layers having magnetostriction constants different from each other and disposed so as to partially overlap each other so that occurrence of noise due to a stress-induced anisotropy effect can be suppressed (refer to, for example, JP-A No. H07-014120); and a thin film magnetic head including a pole chip having zero or negative magnetostriction constant and a head core rear part having zero or positive magnetostriction constant so as to be able to suppress distorsion of a reproduced waveform (refer to, for example, JP-A No. H02-252111).
Further another example is a thin film magnetic head having a magnetic domain control soft magnetic layer for making a 180° magnetic wall in the core width direction appear in a magnetic domain structure of a yoke between a coil covering layer which covers a coil layer and the yoke in a magnetic pole layer so that an excellent magnetic domain structure, a high frequency response characteristic, and a high transfer rate can be assured (refer to, for example, JP-A No. 2000-331310).
In order to assure the operation characteristics of the thin film magnetic head of the perpendicular recording method, it is necessary to optimize the magnetic domain structure of the magnetic pole layer also from this viewpoint of suppressing unintended erasure of information at the non-recording time. The “unintended erasure of information at the non-recording time” is a trouble in the recording characteristic such that information recorded on a recording medium is erased unintentionally by leakage of a magnetic flux (remanent magnetization) remaining in the magnetic pole layer due to the magnetic domain structure of the magnetic pole layer as a part for emitting a magnetic flux for recording at the non-recording time, that is, in a state where the thin film coil is not energized (no magnetic flux for recording is generated). Although it is known that the composition of the magnetic material and magnetostriction of a magnetic component exert an influence on the magnetic domain structure of the magnetic pole layer, sufficient knowledge regarding the relation between an unintended information erasure occurrence mechanism at the time of non-recording time and the magnetic domain structure of the magnetic pole layer is not obtained conventionally. It is consequently an issue how to set the magnetic domain structure of the magnetic pole layer in order to suppress unintended erasure of information at the non-recording time. Therefore, to assure the operation characteristics of the thin film magnetic head of the perpendicular recording method, establishment of a technique capable of suppressing unintended erasure of information at the non-recording time is demanded.